1. Field of the Invention
The present invention relates to a thin film semiconductor device, an electronic device using the same, and a manufacturing method thereof. More particularly, the present invention relates to a thin film semiconductor device with improved durability to be mounted on a flexible substrate, an electronic device using the same, and a manufacturing method thereof.
2. Description of the Related Art
Conventional flat panel display devices, such as a thin film transistor-liquid crystal display (TFT-LCD) and a thin film transistor-organic light emitting diode (TFT-OLED), generally form thin film semiconductor devices of amorphous silicon-TFT or polysilicon-TFT on glass substrates. Recently, studies on the possibility of substituting flexible substrates, such as plastic substrates, for the glass substrates of the flat panel display devices have been performed. A flexible substrate for a flat panel display device has advantages of durability, lightweight, and flexibility so that the flexible substrate may be used for a mobile device. However, in a case in which semiconductor chips are formed on a flexible substrate, the semiconductor chips may be broken due to bending or folding of the flexible substrate. A conventional TFT-LCD includes a polysilicon-TFT formed of an inorganic thin film. In this case, since the elastic coefficient of a TFT portion is large, the TFT-LCD may be easily broken when the TFT is slightly transformed due to bending of the flexible substrate. However, since the TFT occupies about 1% of the entire area of a unit pixel, transformation of the TFT should be prevented in order to prevent breakage of the semiconductor device due to transformation of the TFT by the bending of the flexible substrate.
FIG. 1 illustrates a sectional view of a conventional TFT-LCD for preventing deformation of a TFT.
Referring to FIG. 1, a structure is formed in a substrate of a flexible acrylate copolymer film 1, and a gate electrode 5 is formed on a lower portion of a cradle. An insulating layer 6 formed of a dielectric material, such as silicon nitride (SiN) or silicon oxide (SiO2), is formed on an upper surface of the substrate 1 including the gate electrode 5. An active layer 10, which is formed of an amorphous silicon, is formed on a portion of the insulating layer 6 on the gate electrode 5. In addition, silicon layers 12 and 13 that are doped of n-type or p-type ions are formed on corners of the active layer 10 and the insulating layer 6 on the gate electrode 5 in order to expose the active layer 10. A drain electrode 14 and a source electrode 15 are formed on the doped silicon layers 12 and 13, respectively. A first metal 16 is connected to the drain electrode 14 to extend the drain electrode 14. A second metal 17 is connected to the source electrode 15 to connect the source electrode 15 to a wall of the structure. A dielectric material 18 that planarizes the substrate 1 is formed on the entire structure.
The conventional TFT includes the cradle structure to disperse stress due to bending of the substrate 1. However, external stress is concentrated on the thin film due to the high elastic coefficient of the thin film that forms the TFT, so the dispersion of the stress due to the cradle structure is slight. More particularly, the conventional TFT cannot supplement the material property of the TFT, so the durability of the electronic device including the TFT cannot be improved.